Electrical connecting fixture



May 3, 1949.

T. M0 L. DAVIS ELECTRICAL CONNECTING FIXTURE Filed April '7, 1945 glwue/wtom THOMAS M LELLAN DAVIS MWLW Patented May 3, 1949 UNITED STATES PATENT OFFICE (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 4 Claims.

This invention relates to electrical connecting fixtures, and more particularly to a grounding fixture for high frequency electrical apparatus.

In electrical apparatus, and particularly high frequency electronic apparatus, it may be desirable to maintain some of the components of the apparatus at a substantially uniform round'potential. Where the apparatus is to be operated at low frequencies, the impedance resulting from the resistance and reactance of the grounding path may not be suilicient to seriously impair the efficiency of the grounding connection. However, where the apparatus is to be operated at high frequencies, the impedance of the ground path may become a very important factor and may be suilicient to make a suitably uniform ground potential .at the several components connected thereby diflicult to obtain.

Since steel possesses very desirable structural features as compared with copper and other similar conductive materials, it is often selected as the chassis material. Steel, however, is a much poorer conductor than copper and consequently presents a higher resistance. Similarly aluminum, because of its lightweight, may be employed as the chassis material although its electrical conductivity is also substantially lower than copper. Both steel and aluminum when used in high frequency apparatus present high contact resistance and, in addition, the latter does not readily permit the use of other than pressure contact connections, it not being adaptable to ordinary soldering procedure. Efforts have been made to coat steel or aluminum with a material having a lower resistance such as silver in order to provide a low resistance electrical path, but considerable difiiculty has been encountered in obtaining a satisfactory coating. Also the coating process is undesirably expensive.

Further difficulty in obtaining a suitably uniform ground potential in electronic apparatus to be operated at high frequencies may be encountered where, in order to provide required structural strength, it is necessary to employ relatively thick tube sockets. In such cases the length of the leads connecting the terminal or terminals of the socket to be grounded to the chassis may result in considerable impedance at high frequencies and this may result in a relatively ineflicient ground connection.

An object of the present invention is to provide an effective and eflicient grounding fixture for use in high frequency electronic apparatus.

In accordance with one embodiment of this invention as employed with tube sockets, a grounding fixture may comprise a plate of highly conductive material, which is mounted on the apparatus chassis adjacent the sockets to be grounded and is provided with suitable apertures to receive the tube sockets. Two side members extend away from the chassis at substantially right angles and are integrally formed with two parallel edges of the plate. The lower portions of the side members are bent inwardly to bring the lower edges of the fixture either into direct contact with one or more of the soldering socket terminals, or close enough to permit soldering a short connecting lead therebetween.

Other objects and advantages of the'present invention will be apparent from the following detailed description taken in conjunction with the drawings, wherein:

Fig. 1 is a perspective view of the underside of a portion of an electronic apparatus chassis, having a grounding fixture constructed in accordance with this invention mounted thereon;

Fig. 2 is an enlarged, vertical, sectional view along the line 2-2 of Fig. 1; and

Fig. 3 is a view similar to Fig. 2 showing, however, the grounding fixture directly connected to a soldering terminal.

Referring now to the drawings, and particularly to Fig, 1 thereof, a plate 5 of suitable structural material is there shown which forms a base for the apparatus chassis. For purposes of illustration, two tube sockets 6 having annular grooves 1 formed about the peripheries of each of the upper portions thereof are shown mounted in apertures 8 formed in the base plate 5. An annular shoulder 9 is formed about the upper portion of each of the tube sockets 6 immediately above the annular groove 1' and the lower side of each shoulder rests on the upper surface of the base plate 5. The sockets are retained in position in the apertures 8 by flexible snaprings l0 positioned in the annular grooves I. These snaprings engage the lower side of the base plate 5.

In order to obtain required structural strength, the sockets 6 are made relatively thick, and the lower portion of each of the sockets extends a substantial distance below the level of the base plate 5, as shown in Figs. 1, 2, and 3. Each of the tube sockets is provided with a plurality of soldering terminals l2 which extend downwardly from the base thereof.

Ordinarily, in order to ground one of the terminals l2 to the base plate 5, a lead would be connected between the terminal to be grounded and the base plate. It would, of course, then be necessary for the base plate to be made of a conductive material. It will be apparent that the ground path between two terminals to be grounded would then include the two leads connecting the terminal to the base plate and the base plate itself. Where the apparatus of which these tube sockets are a part is to be operated at high frequencies, as hereinbefore pointed out, the impedance of the grounding leads as well as the impedance of the base plate may become a very considerable factor in determing the efficiency of the ground path. It is, of course, desirable to provide a ground path having as low an impedance as possible in order to maintain the several terminals to be grounded at a substantially uniform ground potential.

In accordance with this invention, in order to provide a grounding fixture which will afford a low impedance ground path between the several components of the apparatus to be grounded while permitting the use of chassis material having desirable structural properties, a rectangular, metal, channel plate l3 of U-shaped cross section is mounted on the underside of the base plate 5. The material of which this plate is made is selected with reference primarily to its electrical conductivity rather than with reference to its structural strength since the structural strength required is provided by th base plate 5. Apertures M are formed in this plate and are so located therein as to correspond in position, when the plate is assembled on the base plate 5, to the position of the apertures 8 formed in the base plate 5.

As shown in Fig. 2 a pair of side members l5, integrally formed. with the cross portion iii of the grounding fixture i3, extend downwardly a distance substantially equivalent to the distance between the underside of the plate 5 and the lower ends of the terminals l2. Each of the side members i5 is provided at its lower edge with an inwardly extendin portion l7. Ground connection to the socket terminal to be grounded is then made either by soldering a very short lead, such as the lead l8, shown in Fig. 2, to the inner edge of the member E7, or as shown in Fig. 3, by makan inwardly extending portion l9 shown in Fig. 3, and corresponding to the portion I! of Fig. 2, long enough so that the terminal to be grounded need be bent only slightly to engage the edge thereof. The terminal may then be soldered to the edge. While the latter method is the more desirable, it will be apparent that even where a lead must be connected between the portion I1 and the terminal to be grounded, it will usually be practicable to employ a very short lead and consequently little additional impedance will be presented thereby.

Where several sockets or components of the apparatus are grounded to a grounding fixture in accordance with this invention, it will be apparent that not only is a very short lead or no lead at all required to connect each of the components to the grounding fixture but that by employing a grounding fixture of highly conductive material, a very low impedance path is provided between the several components irrespective of the conductivity of the material of which the base plate 5 is made. Also, where the grounding fixture is made U-shaped in cross section, as shown, the rounding fixture I3 serves as a radio frequency shield for the lower portions of the sockets 6.

While but one embodiment of this invention has been shown and described, it will be understood that many changes and modifications may be made therein without departing from the spirit or scope of the present invention.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without payment of any royalty thereon or therefor.

What is claimed is:

1. In high frequency radio apparatus comprising vacuum tube components and sockets therefor; the combination of, a main chassis member apertured to receive the vacuum tube sockets, a low impedance high frequency conducting channel plate mounted on said chassis and formed with apertures therein registering with corresponding apertures in said chassis, and conducting means for connecting predetermined terminals of said sockets to said channel plate.

2. In high frequency radio apparatus comprising a multiplicity of components therefor, each havin at least one terminal associated therewith, a main chassis member on which said components are supported apertured to receive said multiplicity of components, a low impedance high frequency conducting channel plate mounted on said chassis and formed with apertures therein registering with corresponding apertures in said chassis through which the portion of said multiplicity of components supporting the said terminals extend, and means for connecting predetermined terminals associated with said multiplicity of components to said channel plate.

3. In high frequency radio apparatus comprising a plurality of components each having at least one terminal associated therewith, a main chassis member on which said components are supported apertured to receive said components and means for establishing a ground connection for predetermined terminals of said components and for shielding said terminals comprisin a C-shaped conducting plate of low impedance to high frequencies mounted on said chassis formed with apertures therein registering with corresponding apertures of said chassis adjacent to said terminals and electrically connected to said terminals, the sides of said plate being disposed on opposite sides of said terminals.

1. In high frequency radio apparatus comprising a multiplicity of vacuum tube components and sockets therefor, said sockets being of the type which are adapted to spring lock in the aperture of a chassis; the combination of, a main chassis member apertured to receive said tube sockets, a low impedance high frequency conducting channel plate mounted on said chassis and formed with apertures therein registerin with corresponding apertures of said chassis whereby the spring locking means of said sockets may be employed to secure the channel plate to said chassis and conducting means for connecting predetermined terminals of said sockets to said channel plate.

THOMAS McL. DAVIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,747,938 Hull Feb. 18, 1930 1,909,685 Kenney May 16, 1933 2,017,549 Salzberg Oct. 15, 1935 2,135,672 Morris Nov. 8, 1938 2,312,181 Matthews Feb. 23, 1943 2,376,625 Schmitt May 22, 1945 

